With growing demands to a mass memory, a nonvolatile memory has been used widely. As a major factor which impedes realization of a large-capacity nonvolatile memory, there is increase of a chip cost due to increase of chip area. For reduction of the chip area of a nonvolatile memory, a MONOS single transistor memory is proposed (for example, refer to Patent Document 1). The MONOS single transistor memory is formed by one bit per one transistor (MONOS stands for Metal Oxide Nitride Oxide Semiconductor).
[Patent Document 1]
    Japanese Unexamined Patent Publication No. 2006-185530